JPH10309167A - Continuous sterilization of cereals and equipment therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously sterilize cereals by utilizing their own volatile components such as moisture without adding additives, by feeding and cold- conveying cereals into the extruder, heat-kneading them and feeding and cold- extruding out of the extruder. SOLUTION: The cereals are fluidized and continuously sterilized by means of an extruder. This sterilization process comprises a step in which the cereals are fed into the extruder and cold-conveyed, a step in which the cereals are kneaded in an atmosphere formed by the volatile components liberated from the cereals, and a step in which the heat-treated cereals are fed and cold- extruded. The temperature at which the cereals are cold-extruded is preferably room temperature to 80 deg.C. The cereals preferably do no fluctuate the α-degree of the starch in the grains substantially, while the cereals are cold-extruded out of the extruder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for continuously sterilizing cereals, and more particularly to a method and an apparatus for continuously sterilizing cereals using an extruder.

[0002]

2. Description of the Related Art Grains such as buckwheat, wheat, rice, and their processed products such as buckwheat, flour, potato starch, new flour, corn flour, defatted soy flour, and rice bran are marketed as major foods. It is important to maintain and preserve the quality of these cereals. Usually, these cereal powders contain 10% by weight or more of water, and the oxidation of fatty acids in the cereals progresses due to oxidation reaction derived from microorganisms and the like, so that the flavor may be impaired and the quality may be degraded. For this reason, it is necessary to perform treatments such as sterilization to prevent deterioration and flavor from being caused by microorganisms.

Conventionally, as an example of a sterilization method, a sterilization method using superheated steam is known. In this method, cereal powder is put into superheated steam flowing through an air flow pipe and then instantaneously sterilized during transfer.
~ 3 kg / cm ² G, temperature 120 ~ 260 ℃, residence time 5 ~ 10
Sterilization is performed under the conditions of sec. Although the number of general viable bacteria and the number of heat-resistant bacteria are reduced by this method, the flavor is impaired,
In addition, in the case of rice bran with a high fat content, clogging may occur in the airflow tube and the operation may become impossible.

As another example of the sterilization method, a high-pressure sterilization method using an autoclave is known. In this method, spores can be sterilized by heating to 100 ° C. or more by pressurized steam in an autoclave. However, if the water content is insufficient, the sterilization efficiency is poor and the flavor cannot be maintained.

Further, as a method of sterilizing and maintaining the flavor, a method of using an extruder and sterilizing by heating at a low temperature, low moisture and for a short time without deteriorating the quality of grains such as flour is known. JP-A-62-2
205759). According to this method, when the powder is kept in a fluidized state and passed through the extruder by rotating a screw, 0.5 to 5% by weight of ethyl alcohol is added, and the low water content is added by utilizing the complementary sterilizing action of ethyl alcohol. Under the conditions, the product is heated and extruded so that the outlet temperature is 55 ° C or less.

[0006]

However, even in the method using an extruder, since ethyl alcohol is added, there is a problem that the original flavor of the cereal itself cannot be sufficiently maintained. For example, it was not sufficient for grains having a unique flavor such as buckwheat flour. In addition, when the temperature is reduced to a low temperature, low in moisture and heated for a short time in order to maintain the flavor, there is a problem that sterilization of heat-resistant bacteria and the like is not sufficient.

SUMMARY OF THE INVENTION The present invention has been made to address such a problem, and in germicidal treatment of cereals, continuous use of volatile components such as water contained in the cereals themselves without adding additives. It is an object of the present invention to provide a method and an apparatus for continuously sterilizing cereals without impairing the flavor.

[0008]

The continuous sterilization method for cereals of the present invention is a continuous sterilization method for continuously sterilizing cereals in a fluidized state by an extruder, wherein the cereals are filled in the extruder. The process is characterized by including a process of cooling and transferring while performing the process, a process of kneading and heating the grains, and a process of cooling and extruding while filling the grains.

[0009] The kneading and heating step is characterized in that the kneading and heating are performed in an atmosphere formed by volatile components that generate grains. Here, the volatile component generated by the cereal refers to a component that can be volatilized under the conditions of the kneading and heating step, among components originally contained in the cereal itself and components contained in the storage environment. Such volatile components include water and the like.

The temperature of cereal extruded in the step of cooling and extruding is from room temperature to 80 ° C.

[0011] Further, the grains extruded by cooling are characterized in that the degree of pregelatinization of starch contained in the grains does not substantially fluctuate. Here, that the degree of pregelatinization does not substantially fluctuate means that the pregelatinization degree of the starch contained in the raw cereal grains is in a fluctuation range not exceeding + 10% before and after the continuous sterilization treatment. The degree of pregelatinization refers to a value measured by the diastase method.

The continuous grain sterilizer of the present invention is an extruder-type grain continuous sterilizer having a plurality of continuous barrels and screws provided in these barrels, wherein the extruder comprises: A cooling transfer section, a kneading and heating section, and a cooling extrusion section are formed in this order from the grain supply section side, and a screw body in which a screw is fitted to a screw shaft core and a connected body of a disk body composed of at least one disk piece. At least a forward screw body and a disc body are arranged in the cooling transfer section and the cooling extrusion section, and at least a kneading disc body is arranged in the kneading and heating section.

Further, the extruder is a two-shaft extruder, and the screw has a double-supported structure that supports the rotation axis of the screw shaft at the tip end of the outlet.

By having a step of filling and cooling cereals before and after the step of kneading and heating with an extruder,
The volatile components, especially water, contained in the cereals are continuously supersaturated in the extruder and can be sterilized. Also,
Even in this state, the grains maintain a fluidized state,
Variations in the degree of pregelatinization of starch contained in cereals can be kept low. According to the present invention, other additives such as alcohols are not added to cereals, and the volatilization of volatile components contained in the cereals can be suppressed, so that the unique flavor of the cereals themselves is maintained. can do.

In the present invention, sterilization is performed at room temperature.
It refers to reducing bacteria contained in raw cereals to a level that does not cause deterioration in quality even if cereals are stored for more than one month.Specifically, flour that is frequently used as a food material in cereals It means that the number of general viable bacteria is at the same level. More specifically, it means that the number of general viable bacteria is at a level of 10 ² to 10 ³ cells / g. The flavor is a sensation including scent, smell, texture and the like, and particularly refers to the scent and smell of the raw cereal grains.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the continuous cereal sterilizer of the present invention will be described with reference to FIGS. FIG. 1 is a view showing a continuous sterilizing apparatus, and FIG.
(B) and FIG. 2 (c) are perspective views of a disk body in which a plurality of disk pieces are connected, and FIG. 3 (a) shows a state where the screw body and the disk body are fitted to the screw shaft core. FIG. 3B is a perspective view showing a screw. As shown in FIG. 1, the continuous sterilizer of the present invention is an extruder-type sterilizer, and includes a barrel 2 having a screw therein, a motor 3 for driving the screw, a raw material supply unit 4, and a raw material discharge unit (shown in FIG. 1). Are omitted) and a shaft fixing portion 5 that supports the screw. The continuous sterilizing apparatus of the present invention is preferably a multi-screw extruder having a plurality of screws, and more preferably a twin-screw extruder having two screws. In the case of a twin-screw extruder, it is preferable that the screw has a double-supported structure that supports the rotation axis of the screw shaft at the outlet end portion. With such a double-sided structure, grains can be sufficiently filled and cooled before and after the kneading and heating unit.

In the case of a twin-screw extruder, for example, the screws are arranged in parallel in the barrel 2 in plan view. For example, in the case of a twin-screw extruder, the barrel 2 has a cocoon shape in a cross-sectional view perpendicular to the screw shaft, and two screws are provided inside the cocoon shape. Further, as shown in FIG. 1, the whole is divided into a plurality of parts so that the temperature and pressure in each barrel can be detected. The temperature inside the barrel is adjusted to an arbitrary temperature by a heating device provided outside the barrel using electric heat or high-temperature steam, and a cooling device such as water cooling or air cooling.

In the continuous sterilizing apparatus according to the present invention, the temperature of the grains in the cooling transfer section and the cooling extruding section can be reduced by the heating apparatus and the cooling apparatus, and the temperature of the grains in the kneading and heating section can be increased. Since the cereals are continuously transferred as a whole in the barrel, the temperature of the barrel does not match the temperature of the cereals in the barrel. Therefore, the boundaries of the cooling transfer section and the kneading and heating section do not always coincide with the boundaries of the barrels performing cooling and heating. In the continuous sterilization apparatus of the present invention,
The screw pattern is such that a packed bed of grains can be formed at both ends of the kneading and heating unit.

As shown in FIGS. 2 and 3, the screw 1 is composed of a screw 7 and a disk 8 connected to a screw shaft 6. The screw body 7 includes a forward screw body for moving grains in the barrel forward and a reverse screw body for moving backward.
The disc body 8 is a kneading disc body for kneading and shearing grains in the barrel 2 by combining a plurality of disc pieces 8a having the same or different thicknesses, a forward disc body for advancing, or a reverse disc body for retreating. It can be. That is, when a plurality of disk pieces 8a having a convex portion 8b and a concave portion 8c with respect to the circumferential surface are prepared and fitted and connected on the screw shaft 6, the screws are connected in a plan view. By arranging the disk pieces 8a in order such that the trajectory of every other convex portion 8b or concave portion 8c is parallel to the axis, a kneading disk body having a kneading / shearing function can be obtained (FIG. 2 (b)). Further, by arranging the disk pieces 8a in order such that the locus of the connected protruding portion 8b or concave portion 8c has a predetermined angle with respect to the axis, a forward disk or a reverse disk can be obtained. (FIG. 2C). In addition, even if it is a kneading disk body, the disk piece 8a
By forming a taper on the circumferential surface of the disk, a forward disk or a reverse disk can be obtained. By connecting the screw body 7 and the disk body 8 to each other, the screw 1 can be brought into any state such as transferring, filling, kneading, and extruding cereals in the barrel. Further, these states can be arbitrarily combined.

In the continuous sterilizing apparatus of the present invention, at least a forward screw body and a disk body are arranged in the cooling transfer section and the cooling extruding section, and at least a kneading disk body is arranged in the kneading and heating section, so that the kneading and heating section is located before and after the kneading and heating section. And sterilization can be performed continuously in a fluidized state while filling the grains.

The continuous sterilization method of the present invention for continuously sterilizing cereals will be described. This continuous sterilization method is performed using an extruder. As the extruder to be used, any extruder that can be cooled and transported while filling grains, kneaded, heated, and cooled and extruded while filling grains can be used. Preferred extruders include the above-described multi-screw extruders, and more preferably, a twin-screw extruder having a double-ended structure. With the above-described twin-screw extruder, the grains fluidized inside the barrel of the extruder reduce the flow velocity due to the contact resistance of the barrel surface, and the entire body draws a gourd trajectory with a constantly reversing movement and a screw body and It is transferred and filled, kneaded, heated and filled and extruded while being divided into two parts by a screw composed of a disk body. Therefore, it is possible to easily perform the sterilization treatment while forming the filling layer before and after the kneading and heating. In addition, temperature control can be easily performed.

The step of cooling and transferring cereals according to the present invention while filling the cereals is a step of forming a packed bed while the cereals supplied from the raw material supply unit are transferred in the barrel. The cooling in this step is to prevent the grains having the packed layer formed therein from being heated in the barrel and to prevent the starch from undergoing gelatinization and denaturation. As the barrel temperature, it is preferable that the temperature of the raw material supply section is from room temperature to about 60 ° C. and the temperature of the barrel connected to the barrel is equal to or lower than the temperature of the kneading heating section. This is because the filling layer is effectively formed without raising the temperature of the grains in the barrel, and the next kneading and heating is performed.

The transfer of the grains and the formation of the packed bed in the barrel can be performed by selecting the shape and combination of the screw body and the disc body. In the step of cooling and transferring while filling grains, it is preferable to use a screw in which at least a forward screw body and a disc body are combined. As the disk, a kneading disk is particularly preferable. The grains are transported by the forward screw body, and the packed bed is formed by the kneading disk body. In order to increase the degree of filling of the filling layer, a reverse disk body can be combined.

The step of kneading and heating cereals according to the present invention comprises:
This is a process of continuously sterilizing by heating cereals, which are confined between the two packing layers formed in the barrel, while maintaining the grains in a fluidized state. In the present invention, it is preferable that kneading and heating be performed in an atmosphere formed by volatile components that generate cereals without adding other substances such as moisture and alcohols at the time of supplying raw materials or during kneading and heating. Examples of the volatile components generated by cereals include water, aroma and odor components. In the present invention, a cereal having a water content of about 1 to 20% by weight, preferably about 3 to 18% by weight can be continuously sterilized with only the water of the raw cereal. Further, the fluidized state can be maintained under heating.

The heating temperature depends on the type and shape of the cereal, but in the sterilization method using an extruder,
Any temperature can be used as long as it can be sterilized under the moisture content of the cereal without causing denaturation of the starch and without impairing the flavor. The starch quality of the cereals is liable to easily cause gelatinization and α-denaturation as the water content increases, but in the present invention, the equilibrium water content of the cereals themselves or higher is not used in the kneading and heating step, The temperature at which sterilization can be performed can be set generally higher than the gelatinization start temperature of about 60 ° C. Specifically, the processing volume of cereals is 50-250kg /
For extruders of the order hr., set the barrel temperature to 8
It is preferable to set the temperature to 0 to 220 ° C, preferably 100 to 200 ° C. In this case, the average temperature of cereals will be about 40-80 ° C.

In the step of kneading and heating the grains, it is preferable to use a screw incorporating at least a kneading disk. By incorporating the kneading disk body, the grains can be kneaded and heated while effectively taking in the heat of the barrel and effectively performing heat exchange. In addition, depending on the type and shape of the grains, a forward disk, a reverse disk, a forward screw body, or the like can be combined with the kneading disk.

The step of cooling and extruding grains while filling the grains according to the present invention is a step of cooling and extruding the sterilized grains while forming a packed layer. The formation of the packed bed and the cooling extrusion of grains can be performed by selecting the shape and combination of the disc body and the screw body. In this step, it is preferable to use a screw in which at least a forward screw body and a disc body are combined. The grains can be extruded from the extruder while sufficiently cooling the grains during extrusion. A preferred combination is a forward screw body and a kneading disc body. Instead of the kneading disk, a forward disk which can reduce the amount of grain to be extruded may be used alone or in combination.

The cooling in this step may be any cooling method capable of keeping the temperature of the grains extruded from the extruder at room temperature to 80 ° C. By setting this temperature, the grains extruded from the extruder can be sterilized without impairing the flavor and without volatilizing volatile components such as water contained in the raw grains. As a specific cooling method, the cereals are set at 80 ° C by setting the barrel temperature at room temperature to 50 ° C, preferably at room temperature to 40 ° C.
It can be:

The method for continuously sterilizing cereals according to the present invention comprises the steps of:
This is a method in which the degree of conversion is not substantially changed. By not substantially changing the degree of α-formation, the unique flavor of each cereal can be maintained. As a method for substantially preventing the degree of pregelatinization from fluctuating, any method may be used as long as the amount of water is reduced in the step of kneading and heating the grains so as to maintain the grains in the barrel in a fluidized state. Specifically, in the kneading and heating step, a kneading disk body is disposed, and a filler layer is provided before and after the kneading and heating, whereby a change in the degree of α-formation can be suppressed.

An example of a screw pattern suitable for the method for sterilizing cereals of the present invention will be described with reference to FIG. FIG. 4 is a schematic diagram of a screw pattern in a biaxial extruder having a double-sided structure and a diagram showing a set temperature state of a barrel divided into six. Screw patterns A, B and C are:
The forward screw 7a, the kneading disk 9 and the forward disk 10 are connected to each other. In the barrel 2, the raw cereal supply section 11 and the extrusion outlet 12 are cooled, and the intermediate section 13 is heated. With such a barrel temperature setting and screws having screw patterns A, B and C,
The cooling transfer section and the packed bed composed of the forward screw body 7a and the kneading disk body 9, the kneading and heating section composed of at least the kneading disk body 9, and at least the kneading disk body 9 and / or the forward screw body A packed bed composed of 7a and a cooling extrusion can be formed in the barrel.

The extrusion conditions of the twin-screw extruder suitable for the sterilization method of the present invention are as follows.
In the case of an extruder of about 0 kg / hr., The screw rotation speed is 50 to 300 rpm, preferably 90 to 160 rpm, and the residence time in the barrel is 20 to 100 seconds, preferably 30 to 60 seconds.

The sterilizing method and the sterilizing apparatus according to the present invention are:
The method can be applied to cereals, and the starch contained in the cereals can be applied regardless of the content of amylose or amylopectin. Such cereals include rice, corn, sorghum, wheat, barley, naked barley, oats, rye, buckwheat, millet, leeches, millet, village potatoes, potatoes, lilies, cat chestnuts, chestnuts, wrinkled peas, kuzu, sweet potatoes , Mountain potato, soybeans, red beans, broad beans, kidney beans, peas, tapioca,
It is applicable to mung bean and the like, and is particularly suitable for disinfecting cereal powders obtained by pulverizing these cereals, such as defatted soybean powder, buckwheat flour, rice flour, rice bran, corn flour, and potato starch powder. It can also be used for sterilization of pharmaceutical powders containing starch used for sugar-coated tablets and the like. Furthermore, it can be applied to spices such as pepper, pepper, curry powder, nutmeg and the like.

[0033]

【Example】

Examples 1 to 7 and Comparative Examples 1 to 2 As a two-axis extruder having a double-sided structure, an alpha riser type 100 (trade name, manufactured by Suehiro EPM Co., Ltd.) was prepared, and FIG. And the sterilization treatment was continuously performed using buckwheat flour as a raw material cereal. Table 1 shows the operating conditions of the sterilization treatment. The raw buckwheat flour before sterilization is 1.2 × 10
^A viable count of ⁶ bacteria / g was included, and the coliform group was positive. The water content is 13.5% by weight, and the degree of pregelatinization is
69.8%. The characteristics of the buckwheat flour after the treatment were evaluated by the following methods. Table 1 shows the evaluation results.

1) Moisture Content The buckwheat flour after the treatment was measured with a moisture meter FD-230 (trade name, manufactured by Kett). 2) Bacterial count Using a Petrifilm AC plate (trade name, manufactured by 3M Healthcare Co., Ltd.) as a general viable cell count analysis plate, the viable count in the buckwheat flour after the treatment was measured by the standard agar plate medium method. 3) Flavor The aroma and smell of the buckwheat flour after the treatment were measured by a sensory test. In the sensory test, 5 g of buckwheat flour and 10 g of hot water
Was added, and the mixture was uniformly kneaded, and the evaluation was performed by comparing the aroma and odor of the buckwheat flour by five panelists with the buckwheat flour before the treatment. Evaluation points are shown by rounding the average of five panelists. The evaluation criteria were 5 when the scent and odor of the buckwheat flour were the same as before the treatment, and 4 when the scent and scent of the buckwheat flour were not the same as before the treatment, and the scent of the buckwheat flour was 4 The evaluation score was 3 when the odor was felt weak, 2 when the fragrance and odor of the buckwheat were faint, and 1 when the fragrance and odor of the buckwheat were not felt at all. 4) Degree of α-formation The buckwheat flour after the treatment was measured by the above-mentioned diastase method.

[0035]

[Table 1]

As shown in Table 1, the buckwheat flour treated in Examples 1 to 7 had a bacterial count ranging from 10 ⁶ / g before treatment to 10 ² to 10 ³ / g. The amount decreased and sterilization could be performed. In Example 7, the heat-resistant bacteria were 3
00 cells / g, coliform group was negative. In addition, the obtained buckwheat flour had a small change in the degree of pregelatinization, a small decrease in the water content of the raw buckwheat flour, and was also excellent in flavor. In Comparative Examples 1 and 2, the grain temperature to be extruded was 80 ° C.
, The flavor was impaired.

[0037]

According to the continuous sterilization method of the present invention, a step of cooling and transferring while filling cereals using an extruder;
Since it includes the step of kneading and heating and the step of cooling and extruding while filling, it is possible to sterilize continuously and without impairing the flavor by utilizing volatile components such as moisture contained in the cereal itself.

Further, since the step of kneading and heating is performed in an atmosphere formed by volatile components generated by cereals, continuous sterilization can be performed without adding additives.

Further, since the temperature of the cereal extruded in the step of cooling and extruding is from room temperature to 80 ° C., the flavor is not particularly impaired. Furthermore, since the degree of pregelatinization of the starch contained in the extruded cereal does not substantially fluctuate, sterilization can be performed while maintaining the quality of the raw material.

The continuous sterilization apparatus of the present invention is of an extruder type, in which at least a forward screw body and a disc body are arranged in a cooling transfer section and a cooling extrusion section, and at least a kneading disc body is arranged in a kneading and heating section. Since such a screw is used, cereals can be sterilized continuously and without impairing the flavor by using volatile components such as water contained in the cereals themselves.

Further, by using a biaxial extruder having a double-sided structure, sterilization can be effectively performed in a short time.

[Brief description of the drawings]

FIG. 1 is a diagram showing a continuous sterilization apparatus.

FIG. 2 is a diagram showing a screw body and a disk body.

FIG. 3 is a view showing a screw and its structure.

FIG. 4 is a diagram showing a screw pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Screw 2 Barrel 3 Motor 4 Raw material supply part 5 Shaft fixing part 6 Screw shaft core 7 Screw body 8 Disk body 9 Kneading disk body 10 Forward disk body 11 Raw material supply part side 12 Extrusion outlet side 13 Intermediate part

Claims (6)

[Claims] 1. A continuous sterilization method for cereals in which cereals are continuously sterilized in a fluidized state by an extruder, wherein the extruder cools and transfers the cereals while filling the cereals; A method for continuously sterilizing cereals, comprising a step of kneading and heating, and a step of cooling and extruding while filling the cereals. 2. The method for continuously sterilizing cereals according to claim 1, wherein in the kneading and heating step, the cereals are kneaded and heated in an atmosphere formed by volatile components generated by the cereals. 3. The method for continuously sterilizing cereals according to claim 1, wherein the temperature of cereals extruded in the step of cooling and extruding is from room temperature to 80 ° C. 4. The cereal extruded in the cooling and extruding step, wherein the degree of pregelatinization of starch contained in the cereal does not substantially fluctuate. 2. The method for continuous sterilization of cereals according to claim 1. 5. An extruder-type continuous cereal sterilization apparatus having a plurality of continuous barrels and screws provided in the barrels, wherein the extruder includes a cooling transfer unit, a kneading and heating unit, And a cooling extrusion section are formed in order from the grain supply section side, and the screw is constituted by a connection body of a screw body fitted to a screw shaft core and a disk body composed of at least one disk piece. A continuous screw sterilizer for cereals, wherein at least a forward screw body and a disc body are arranged in the section and the cooling extrusion section, and at least a kneading disc body is arranged in the kneading and heating section. 6. The cereal grain according to claim 5, wherein the extruder is a twin-screw extruder, and the screw has a double-sided structure that supports a rotation axis of the screw shaft at an outlet end portion. Continuous sterilizer.